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Monday, June 06, 2016

Dear Dr B: Why not string theory?

Dear Marco:
Because we might be wasting time and money and, ultimately, risk that progress stalls entirely.

In contrast to many of my colleagues I do not think that trying to find a quantum theory of gravity is an endeavor purely for the sake of knowledge. Instead, it seems likely to me that finding out what are the quantum properties of space and time will further our understanding of quantum theory in general. And since that theory underlies all modern technology, this is research which bears relevance for applications. Not in ten years and not in 50 years, but maybe in 100 or 500 years.

So far, string theory has scored in two areas. First, it has proved interesting for mathematicians. But I’m not one to easily get floored by pretty theorems – I care about math only to the extent that it’s useful to explain the world. Second, string theory has shown to be useful to push ahead with the lesser understood aspects of quantum field theories. This seems a fruitful avenue and is certainly something to continue. However, this has nothing to do with string theory as a theory of quantum gravity and a unification of the fundamental interactions.

As far as quantum gravity is concerned, string theorist’s main argument seems to be “Well, can you come up with something better?” Then of course if someone answers this question with “Yes” they would never agree that something else might possibly be better. And why would they – there’s no evidence forcing them one way or the other.

I don’t see what one learns from discussing which theory is “better” based on philosophical or aesthetic criteria. That’s why I decided to stay out of this and instead work on quantum gravity phenomenology. As far as testability is concerned all existing approaches to quantum gravity do equally badly, and so I’m equally unconvinced by all of them. It is somewhat of a mystery to me why string theory has become so dominant.

String theorists are very proud of having a microcanonical explanation for the black hole entropy. But we don’t know whether that’s actually a correct description of nature, since nobody has ever seen a black hole evaporate. In fact one could read the firewall problem as a demonstration that indeed this cannot be a correct description of nature. Therefore, this calculation leaves me utterly unimpressed.

But let me be clear here. Nobody (at least nobody whose opinion matters) says that string theory is a research program that should just be discontinued. The question is instead one of balance – does the promise justify the amount of funding spend on it? And the answer to this question is almost certainly no.

The reason is that academia is currently organized so that it invites communal reinforcement, prevents researchers from leaving fields whose promise is dwindling, and supports a rich-get-richer trend. That institutional assessments use the quantity of papers and citation counts as a proxy for quality creates a bonus for fields in which papers can be cranked out quickly. Hence it isn’t surprising that an area whose mathematics its own practitioners frequently describe as “rich” would flourish. What does mathematical “richness” tell us about the use of a theory in the description of nature? I am not aware of any known relation.

In his book Why String Theory?, Conlon tells the history of the discipline from a string theorist’s perspective. As a counterpoint, let me tell you how a cynical outsider might tell this story:

String theory was originally conceived as a theory of the strong nuclear force, but it was soon discovered that quantum chromodynamics was more up to the task. After noting that string theory contains a particle that could be identified as the graviton, it was reconsidered as a theory of quantum gravity.

It turned out however that string theory only makes sense in a 25-dimensional space. To make that compatible with observations, 22 of the dimensions were moved out of sight by rolling them up (compactifying) them to a radius so small they couldn’t be observationally probed.

Next it was noted that the theory also needs supersymmetry. This brings down the number of space dimensions to 9, but also brings a new problem: The world, unfortunately, doesn’t seem to be supersymmetric. Hence, it was postulated that supersymmetry is broken at an energy scale so high we wouldn’t see the symmetry. Even with that problem fixed, however, it was quickly noticed that moving the superpartners out of direct reach would still induce flavor changing neutral currents that, among other things, would lead to proton decay and so be in conflict with observation. Thus, theorists invented R-parity to fix that problem.

The next problem that appeared was that the cosmological constant turned out to be positive instead of zero or negative. While a negative cosmological constant would have been easy to accommodate, string theorists didn’t know what to do with a positive one. But it only took some years to come up with an idea to make that happen too.

String theory was hoped to be a unique completion of the standard model including general relativity. Instead it slowly became clear that there is a huge number of different ways to get rid of the additional dimensions, each of which leads to a different theory at low energies. String theorists are now trying to deal with that problem by inventing some probability measure according to which the standard model is at least a probable occurrence in string theory.

So, you asked, why not string theory? Because it’s an approach that has been fixed over and over again to make it compatible with conflicting observations. Every time that’s been done, string theorists became more convinced of their ideas. And every time they did this, I became more convinced they are merely building a mathematical toy universe.

String theorists of course deny that they are influenced by anything but objective assessment. One noteworthy exception is Joe Polchinski who has considered that social effects play a role, but just came to the conclusion that they aren’t relevant. I think it speaks for his intellectual sincerity that he at least considered it.

At the Munich workshop last December, David Gross (in an exchange with Carlo Rovelli) explained that funding decisions have no influence on whether theoretical physicists chose to work in one field or the other. Well, that’s easy to say if you’re a Nobel Prize winner.

Conlon in his book provides “evidence” that social bias plays no role by explaining that there was only one string theorist in a panel that (positively) evaluated one of his grants. To begin with anecdotes can’t replace data and there is ample evidence that social biases are common human traits, so by default scientists should be susceptible. But even considering his anecdote, I’m not sure why Conlon thinks leaving decisions to non-experts limits bias. My expectation would be that it amplifies bias because it requires drawing on simplified criteria, like the number of papers published and how often they’ve been cited. And what does that depend on? Depends on how many people there are in the field and how many peers favorably reviewed papers on the topic of your work.

I am listing these examples to demonstrate that it is quite common of theoretical physicists (not string theorists in particular) to dismiss the mere possibility that social dynamics influences research decisions.

How large a role play social dynamics and cognitive biases, and how much do they slow down progress on the foundations of physics? I can’t tell you. But even though I can’t tell you how much faster progress could be, I am sure it’s slowed down. I can tell that in the same way that I can tell you diesel in Germany is sold under market value even though I don’t know the market value. I know that because it’s subsidized. And in the same way I can tell that string theory is overpopulated and its promise is overestimated because it’s an idea that benefits from biases which humans demonstrably possess. But I can’t tell you what its real value would be.

The reproduction crisis in the life-sciences and psychology has spurred a debate for better measures of statistical significance. Experimentalists go to length to put into place all kinds of standardized procedures to not draw the wrong conclusions from what their apparatuses measures. In theory development, we have our own crisis, but nobody talks about it. The apparatuses that we use are our own brains and biases we should guard against are cognitive and social biases, communal reinforcement, sunk cost fallacy, wishful thinking and status-quo bias, for just to mention the most common ones. These however are presently entirely unaccounted for. Is this the reason why string theory has gathered so many followers?

Some days I side with Polchinski and Gross and don’t think it makes that much of a difference. It really is an interesting topic and it’s promising. On other days I think we’ve wasted 30 years studying bizarre aspects of a theory that doesn’t bring us any closer to understanding quantum gravity, and it’s nothing but an empty bubble of disappointed expectations. Most days I have to admit I just don’t know.

60 comments:

I don't know about fair or unfair but it doesn't seem quite accurate. For what I can tell (and please keep in mind I'm not a string theorist) most of the effort has gone into expanding the theory, based on arguments that could be summed up as "too big too fail." What any of that has to do with nature has become a secondary question (or maybe not even that).

Great piece. Just one question: in these days that you side with Gross and Polchinski, do you also think that string theory's promise warrants the share of funding it gets? My impression from the rest of the piece was a solid 'no', but then that last paragraph confused me.

Thank you a lot for this answer to my question. I am not a string theorist and my attempts on quantum gravity are limited to derive standard quantum mechanics from non-commutative geometry. So, very near your views and very far from strings.

My take is essentially linked to a more general sociological problem in our community: Who decides when a venue is worthwhile to be pursued? What I have learned in more than twenty years of active research is that it does not matter how much you publish, if a few of notable persons will keep you ignoring you just lose.

What does it mean this for people doing research? That a lot of good ideas stay forgotten somewhere in a list of reputable journals. Progress is so stalled until some good soul, in a far future, will let them know.

I learned this from my field, QCD. There has been a lot of activity on understanding how the two-point functions in the Landau gauge behave for a pure Yang-Mills theory.You can read the story on Wikipedia and it is not so good. Just because an important authoritative group imposed their view, the field stayed stuck for several years on a wrong side. Good papers went rejected because did not comply with such a wrong view. This is a generalized problem in physics.

What you see in string theory is just the emerging tip of an iceberg and a severe problem in physis. You just noted it because of the important people that works on it and has a lot of exposure. But there is more and in strong need of fixing.

"I can tell that in the same way that I can tell you diesel in Germany is sold under market value even though I don’t know the market value."

Non-German readers might be a bit confused here. Diesel fuel costs about 10 or 20 per cent less per volume (litre here) than petrol (gasoline or gas to the American readers; I'm reminded of the English colleague who ordered "water with gas" at a bar in the States, to which the bartender replied "Would that be unleaded?"). This originated as a subsidy for heavy vehicles which transport goods. Together with better mileage (both because of the higher efficiency of diesel engines but mainly because there is more energy per volume in diesel than in petrol), diesel cars (probably half the cars in Germany are diesel) consume much less fuel. Road tax is somewhat higher for diesels, but if you drive more than a moderate amount the savings pay off. Since diesel engines generally last longer as well, a diesel probably costs the least over the entire lifetime of the car.

If one sold it, and taxed it, based on the amount of energy it contains or carbon-dioxide produced when burned, it should be more expensive than petrol.

It is basically because of this that there are so many diesel passenger cars in Germany. Although it was more of a publicity stunt, Audi once won the 24-hour Le Mans race with a diesel-powered car.

On these days I still think "no, it doesn't warrant the share of funding it gets", but the "accurate" share (meaning: the share not influenced by social dynamics and cognitive biases) is pretty close to the actual share, so it's just not a large difference.

Yes, I agree, string theory is just a prominent example that has gathered a lot of attention, but the underlying problem is much more general. And it's not a problem that only exists in theoretical physics, it's just that the more detached an area is from experimental test, the more prominent social effects can become.

I think the "only game in town" principle has been a key element in string theory's dominance. As you suggest, there's a lot of theoretical physicists try to get publications quickly, and string theory is the best route. It seems to have become a self-sustaining mountain of maths.

But when you think it took Einstein 8 years to get a single equation correct, what is the chance of the mountain of string theory mathematics actually being correct? 0.001%, I'd say. Not trying to be nasty, just realistic.

Would be fascinating to travel 100 years into the future to discover how the last 30 years of theoretical physics will be viewed by future historians.

Yes, indeed, one could turn the head-count argument around and instead say: if so many smart people haven't yet managed to prove it's the one-and-only right completion of the SM and GR, then that probably means it isn't ;)

And not hestating to call your readers fucked up laymen and imbeciles, not to mention what he writes about you... This man should be held accountable in a court of law, because his slandering is systematic. Sorry, had to get that of my chest. Best.

Very personal and frank answer. Especially social aspects. I agree. Thank you, Bee. I disagree with just one statement. You wrote that “String theorists are very proud of having a microcanonical explanation for the black hole entropy. But we don’t know whether that’s actually a correct description of nature, since nobody has ever seen a black hole evaporate”. However, I believe that this isn't the case. That's not the evaporation. The point is that string theory provides an explanation of the black hole entropy only in the weak(!) coupling regime. They are done for models in flat(!) space-times which are in some sense dual to the string theory on a given black hole background. Since computations are done in a dual(!) theory the physical nature and the location of the (gravitational!) black hole degrees of freedom remain unknown. Moreover, as everybody knows, string computations are not universal.

I usually like Sabine's article but this one is very poor. If I follow the logic we should throw out thing like Electomagnetism because we have patched it a number of times and it still isn't right so out she goes. Then there is some ridiculous argument about we should be improving what gets researched threaded thru an anti string theory rant.

Noa Drake, I read LM's article and LM has gone so far out there it would easily qualify as satire making defamation claims a little hard. I am not sure if he did it deliberately but it would be an obvious defense because it is just so outrageous.

Sabine had a fair crack at half the science fraternity in the article, apparently they are all into communal reinforcement and get rich-quick schemes aren't they :-) String theorists being the worst of the worst apparently. Sabine may not swear and be as crass but she is no less provocative and courting controversy.

I found both articles poor but funny in their own ways as pieces of humour and how not to conduct a science argument.

If you wind Lubos up enough, he wil explode. Like Krakatoa. There will just be a crater left. The sun won't be able to penetrate the cloud cover for six months, many species will die out, but the cost will be worth it because a brighter dawn will come. More string theory articles, please.

First, I have no clue what your problem is with electromagnetism. It's an empirically well established theory, and has been so since a century. Besides this however you seem to have misread my 'cynical history'. What I am saying is merely that reasons which score highly for some people don't score highly for me. And in the absence of evidence, what do we conclude from this?

You ask for a scientific argumentation at the end of your answer. I will provide it :

In 26 dimension String theory, one has to prevent Lorentz invariance violation. This is done by getting rid of mass contributions of the quantum oscillators.This mounts up to making 2 infinite series finite:

1-1+1-1... until eternity

and

1+2+3+4+... until eternity

First a priori argument:

An on going situation which has not ended yet, cannot have a definit outcome.Only when you specify how many steps are to be taken, will you be allowed to assign a fixed number to it.But once you assign the number of steps you will immediately understand that you series is no longer infinit, alas.

Second argument :

1-1+1-1.. etc. is said to be 1/2 (later used to prove the -1/12 outcome of the other series).But this is not an avarage,it is not the avarage of zero plus one, it is a summation that never stops.

Result: the -1/12 cannot be inserted in the formula to yield the 26 dimensions solution. Nothing was solved. There was no proper math done here.

Simply summarized:

Put 1 apple in a basket, take it out again, put it back, take it out again. It will NOT mount up any time soon to become half an apple.Put 1 apple in a basket, then 2, then 3, and you will soon be filling up the entire universe and 'beyond' with apples.

The -1/12 'renormalisation', that's an abnormal situation created by means of human flaw, is made 'normal' again.

This is not a good argument. There is nothing wrong with that type of regularization. And even if you think there is, there are other ways to arrive at the conclusion that you need so-and-so many dimensions to get rid of ghosts.

Having said that, what all these arguments have in common is that they use the standard procedures of quantization. The road not taken is the realization that instead of accepting additional dimensions you could have thrown out the assumption that quantization holds (unmodified) up to arbitrarily high energies.

The bottom line is (to state the obvious) that no proof is better than its assumptions.

A possible solution to the conundrum should indeed have to show that no infinities were needed in the first place. That was the abnormal situation I referred to. Only then will we be rid of ad hoc cut offs.

Two things have bugged me about string theory. The analogy with a classical vibrating string has always puzzled me. When I vibrate a large classical string (say, a few inches long) it has fixed modes of vibration because of the forces acting on that string (gravity, electromagnetic). Now when I get down to the level of strings on string theory, I am told that the analogy still stands: there are fixed modes of vibration, and this can explain the fundamental forces. OK, but what absolutely new forces do we now have to discover to explain the vibration of the strings in string theory? Strings don't move and vibrate without forces. So what's causing the string to vibrate?

Also, if a particle is a string, not a point, then surely it is going to have a whole new host of degrees of freedoms. Stings can deform in so many ways. The limited degrees of freedoms of fermions, say, explains the exclusion principle so elegantly, if particles are strings, doesn't that blow the exclusion principle out of the water? It seems the only way round this is to impose artificial limits on the number of ways a string can deform.

Strings have a tension qua assumption. That is, they have an intrinsic restoring force if you wish. To excite the vibrations, you can use anything that provides energy, in particular a collision of strings that transfer energy and momentum. You don't need any other force for that.

No, it doesn't interfere with the exclusion principle, I don't know why you think so. The particle spin is about representations of the Lorentz-group and string theory doesn't change anything about this. The exclusion principle is basically a consequence of the behavior of certain wave-functions under the Lorentz-group. All that carries over to string theory. Best,

An "intrisic restoring force". Yes, OK. So that's a fifth fundamental force in practice, isn't it? It's not one of the four forces we know. So it must be an unknown fifth force. Isn't it?

As to the exclusion principle, as you know, it says two fermions cannot be in precisely identical states. And the very limited degrees of freedom available to a point particle explains this wonderfully elegantly. But surely a string has so many more degrees of freedom - as an example I look at this diagram from the Wikipedia string theory page which apparently many string theorists will have seen and not corrected:

Well, those strings are deformed completely arbitrarily, which means they have a whole host of additional degrees of freedom. Which surely defeats the exclusion principle as it now becomes very easy for electrons to have slightly different states.

It's not a fifth force, it's the only force - it gives rise to all the other forces (theory of everything and all).

It is right that if you have strings corresponding to different particles (or excitations of particles) then the additional degrees of freedom mean they're not prevented from being in states that are otherwise identical. But that doesn't mean that it becomes 'easy for electrons to have slightly different states' because you need an enormous amount of energy to excite these different states. Basically, it's an effect we'd never see. Best,

My final comment then is that we seem to be exchanging four forces whose mechanisms we understand very well (gauge symmetry) for one force whose mechanism we don't understand - and calling it progress,

Sabine you asked ... "I have no clue what your problem is with electromagnetism. It's an empirically well established theory, and has been so since a century."

How many dimensions in electromagnetism? It also certainly has not been the same for a century, we had classical electromagnetism, then we had Maxwell's equations in curved spacetime and finally Quantum Electrodynamics. The history of electromagnetism got patched between each revolution so we could connect the early theory to the later. That is pretty much the same complaints you make of string theory, I could well imagine until QED was solidified the argument would have been exactly yours that it was a waste of time.

Sabine then you said .. What I am saying is merely that reasons which score highly for some people don't score highly for me. You score doesn't matter to me either so how would you like to settle this heads and tails? Not very scientific but about all we are left with and that is where your article leaves me.

The problem as far as I can see isn't string theory at all, it's the lack of other options. I am not convinced that if someone had a viable idea they couldn't get funding or research time, I would like to hear and see evidence and stories.

So let me pose a question to you at your 'cynical history' level.

Does it matter whether we are researching string theory or 101 other stupid ideas that we already know are not viable? What I mean is we all kind of know we are spinning wheels and treading water waiting for a breakthrough or genius to take us the next step. I saw you have exited from Quantum Gravity because you were sick of beating your head against the wall.

All inquisitiions that start with a demand to be "right" are bound to failure. If a man or a woman were to stand up and claim their right over a territory that would be perfectly understandable, at least down the Amazon river. But this prolonged death of the so called "modern" world and its "culture" that offers nothing in return of the agony before death, how can one perceive it seriously? Do children as well as our students supposedly mild this anxiety? Only when we impose them with our own facade, our way of hiding in plain site. So then, let us enjoy the tribunations of our own accord, the one Arena that we love so much in the absence of which we would be immediately diminished into a mere nothingness.

Classical electrodynamics is a theory which describes nature well, and which has subsequently been generalized to describe it even better, in more general circumstances. String theory, as a theory of quantum gravity and unified interactions, doesn't describe anything that the theories we have wouldn't also describe. I don't understand why you think it's the same situation.

You say: "You score doesn't matter to me either..."

That's the point. You seem to have some trouble understanding what I am saying, so let me spell it out again, very clearly and slowly: In the absence of experimental evidence, what else but opinion is it that people argue with? Nothing. Hence, we better be very careful when evaluating opinions. That is presently not the case.

"The problem as far as I can see isn't string theory at all, it's the lack of other options..."

You're right that the problem isn't string theory at all - the problem is that there is no reason to assume the options that are presently pursued are an accurate reflection of the best options there are.

"I saw you have exited from Quantum Gravity because you were sick of beating your head against the wall."

I don't know what you think you have seen. I have worked for 15 years on quantum gravity phenomenology and still work on that (on and off - I also do other things).

Sabine you said .. " String theory, as a theory of quantum gravity and unified interactions, doesn't describe anything that the theories we have wouldn't also describe. I don't understand why you think it's the same situation."

That isn't quite true and lets give you an example in electromagnetism as it's something we have 3 different versions which similarly describe the same thing.

On light these days we apply Orbital Angular Momentum encoding to a single photon something that can't be described correctly in the classical version, will somewhat work in curved spacetime if you make the time dimension real and works completely in a quantum field description.

There are plenty of other examples of when you are able to join theories, you often get "extra". To me that is what string theory is able to do which is possibly identify the extra, but it may not that is a argument to be had. Whether it is actually physically correct description is totally another question.

Consider the most quoted criticism of string theory, "that it doesn't make any predictions because it can predict just about anything". Well string theory makes a very big prediction that the Standard Model is wrong because it can't derive that model as a stable outcome. So string theory is dead in the grave if the Standard Model doesn't break.

Now I am not here to defend string theory, I am not the right person for that as I really don't believe in it. However I have no better suggestion of what we should be researching and it keeps fundamental science research going which is a good thing.

My point and the bottom line is unless you can argue string theory is starving funding for other possibly viable research then your argument falls flat. I am not sure where you go with your argument which goes, lets stop researching string theory because I judge it bad, but then you don't tell us what you judge good and we should be researching ... there is just this silence.

I feel your pain Sabine that you feel you have wasted 30 years studying, hit a wall and this goes nowhere. If it's conciliation the alternative was to study 101 dumb ideas that hit a not viable wall for 30 years. I guess only you could judge if that would feel better and I do hope you find a new direction soon, e-Hug sent.

"unless you can argue string theory is starving funding for other possibly viable research then your argument falls flat. I am not sure where you go with your argument which goes, lets stop researching string theory because I judge it bad, but then you don't tell us what you judge good and we should be researching ... there is just this silence."

Look, if I told you what you and others *should* be researching, what would be the point of this? I'd obviously just be promoting my own interests. By asking for this, you are totally misunderstanding my intention. I am not telling you there is something wrong with this or that approach, I am telling you there is something wrong with the process of science itself.

I am far from "silent" on what should be done. I have said here and many times before that what needs to be done is to take measures against social and cognitive biases. If people still work in masses on string theory after that, so fine. My point is that presently I plainly can't trust the system - and you shouldn't either. That a lot of people work on string theory and write a lot of papers doesn't tell me anything other than that a lot of people work on string theory and write a lot of papers.

I don't know what your other comments are even about. Yes, joining theories is a good idea, I certainly never said anything to the contrary. But you still have to test that the result actually describes nature, unless you can prove there is only one way to do it. And nothing like that has been proved for string theory, and it will never be proved because we can argue until the end of days exactly what the assumptions of such a proof should be. You cannot derive a theory that describes nature from mathematical consistency alone. It's logically impossible. Best,

Sorry, I missed this one "I feel your pain Sabine that you feel you have wasted 30 years studying, hit a wall and this goes nowhere."

I find it amazing how you continue your attempts to psychoanalyze me, evidently without even bothering to gather the most basic facts. Not only would it seem exceedingly unlikely I'd have spent 30 years studying string theory, given that I'm not yet 40 years old, I have also never worked on string theory, because from the time I came to the field it just smelled sick. In my perception, as someone working on quantum gravity phenomenology, I'm one of the few who have *not* hit a wall. Research is going fine, thanks for asking.

Your comments are exceedingly ill-informed and project opinions on me that I don't hold. It's not a discussion I am interested in continuing.

it is amazing how two opponents are enough to take over the debate... and hide the real points.

If that is not a social bias, what is it? Look first in politics or religions, examples are many; 2 opponents, one endless debate if not war. The only exception I know of is mathematics; any time you have 2 opponents, the same silly game starts and continues forever. Why should it be different in physics?

In facts the two opponents share the very same interest: To make sure that nobody else is part of the game. For this, they decide the nature of the debate, the prerequisites, and the "only two" alternatives that fit with their prerequisites. Then, of course there is no alternative...

In my opinion, the SM is not in a better state than String Theory because none gives (even the hope of) technological output to those who pay. The only thing their proponents can do is to ask for funding. Believe it or not, taxpayers pay for this firstly because they have no choice and secondly because they are presented some successes. The Higgs was really discovered in 1963 or so, and gravitational waves about 100 years ago. When the public realize the true nature of their works, no doubt physicists will have a new perspective in the hanged.

Sabine, a very nice post. From what I understood from David G.'s talk in Munich, String theory is not a theory where you can write down equations on a T-shirt. Its a framework. Does that almost all BSM theories or QG theoriescome under its purview?

Something else and slightly OT, do you know the current status of E8? After Garrett's Lisi's paper form 2007 which caught lot of attention, I haven't seen much followup studies (although I am not up with literature or attend that many conferences any more)There hasn't been a talk at PI also on this recently.

I pretty much disagree with the majority of this post, particularly the tone, b/c there isn't much factual I can take umbrage with and I would say most people working in HEP would agree that its a distortion of how things actually work.

In fact I would point out that the cognitive dissonance might more plausibly go in the opposite direction, rather than simply being attributed to the groupthink of a large quantity of HEP scientists.

Look at the end of the day, people work in string theory, b/c they think it's a promising avenue to describe nature. I simply don't know anyone who works in the field (or really any field) and thinks that their research is a waste of time.

String theory became huge, and remains huge, precisely b/c a very large amount of people think that there is something to it. Speaking purely from the theoretical point of view, I find it hard not to look at it and acknowledge that there really is a lot of 'there' there. That includes many of the unification models that are so tantalizingly close to the real world and the web of relations that it has revealed about physical theories that we already know exist.

As far as being able to test these things, I am much less optimistic. Not b/c string theory is any better or worse than its competitors, but rather that quantum gravity experiment seems like a crapshoot. Indeed reading some of the 'pheno' papers in the QG field makes me despair that anything concrete is going to come out of it within my lifetime. Again, its no one's fault, but the field resembles what observational cosmology was like in the 1800s.

"String theory became huge, and remains huge, precisely b/c a very large amount of people think that there is something to it."

Right. So what?

"I simply don't know anyone who works in the field (or really any field) and thinks that their research is a waste of time."

Three pieces of information about this that you might want to think about.

First: you can have group selection without adapting individuals, simply by excluding those who don't fit. This is how natural selection works too. You don't actually change a member of a species to fit the environment, you simply kill those off who don't fit. That too leads to group that better "fits" the environment.

Second: Humans are very susceptible to group opinion. The more often they hear by other people that something is a good and worthwhile thing to do, the more likely they are to believe it. Look up communal reinforcement.

Third: I did an anonymous survey in 2008 among active researchers in physics in the US/Canada. The results were never published (entirely my fault), but one of the questions I asked was if people would drop their current research project if they would not have to fear for funding difficulties of themselves and their coworkers or students. About a third in hep-the said "yes, immediately" or "yes, after current project is finished". The response rate of that survey was high and the results are representative for the sample.

So maybe the fact that you don't know anybody who thinks their research is a waste of time is because they'd rather bite off their tongue than tell you.

I agree btw, that unfortunately much of what's going on in QG pheno is, erm, low quality. It's a problem, but it's hard to fight as long as there's basically zero money in it. It has gotten much better though in the last years, at least that's my impression.

The very thing you may miss is that there is never a group solution to this problem. The group'gene dies or mutates. The gene is selfish, it has no interest in physics; I guess you read Dawkins. Then String theory to grow the organism - that's why.

Good article Sabine. This sentence jumped out at me: "On other days I think we’ve wasted 30 years studying bizarre aspects of a theory that doesn’t bring us any closer to understanding quantum gravity". You could say this about the standard model.

I have to confess that I am one of those who hoped String Theory (SUSY) would turn out to be a true feature of nature. The reality is we have to accept what the data shows us, and it's apparent that there is an ever narrowing window that it could be an aspect of nature. I do periodically check into Matt Strassler's blog, and from what he says it seems that the window is not yet completely closed.

Not sure what you mean there. We've studied the standard model for 30 years and it hasn't brought us any closer to understanding quantum gravity? Well, why the heck would it? Or did you mean to say that we've studied the standard model for 30 years and haven't learned anything from it? In that case, I think you've missed out some history there. Not only is the standard model dramatically better understood today than at its inception (think of asymptotic freedom, renormalization group, anomaly cancellation, lattice calculations, and so on), predictions derived from it have also considerably improved (and been confirmed to high precision).

You're missing something there, which is that the collective action problem can be overcome with mutual agreements. Look, no scientist really has an incentive to waste the time of their life on something useless. Their own 'selfish' interest is to do good science in the first place. They are hindered in this by the current organization of the system, which prevents any one individually from refusing to play by the rules because they would simply kick themselves out of the system. You break this impasse in the same way that you do it in social situations, by agreeing on regulations or, in this case, guidelines. Why has this not happened? I don't know. It's like scientists don't even want to think about the problem that's in front of their own nose.

Sabine, I don't usually agree with everything you say, but in this post, and the answers to the comments, I think you have been spot on. I completely agree that the comparisons drawn so far with electromagnetism and the standard model don't hold water. Also, without the guide of experiment, we should aim for a counter-institutional-bias mechanism. And it was nice to have the analogy to group selection spelled out.

universe, you could say that about standard model, but for most of the time of development of the standard model, alternatives were alive, funded and lost (steadystate,..etc). I like this article and it touches my fear that string theory pulls too much attention away from thoughtful invention of new solutions and instead constantly trying to make string fit. Lately, I really wonder if String theory is Phlogiston, this might be the frightening verdict of future historians....

A couple of anecdotes to illustrate the general points Bee was making:

1. An acquaintance of mine from when we were PhD students did his PhD on non-string standard model stuff, then got a postdoc at an institute where string theory was prominent and promptly switched to that field. When I met up with him later I asked him why he switched to strings. He smiled and said "Well, you know, that's the way things are going". I can't blame him, he had a wife and kid to support. And it worked out well for him - after one more postdoc he got a permanent faculty job at one of the top uni's in the UK. Would not have happened if he had stuck to his previous non-string field.

2. Another person I know of who also didn't do his PhD on string theory tried his hand at a few different topics in particle theory at the start of his first postdoc. One of them was the topic I happen to work on. He wrote a couple of papers on it that had zero impact, no citations and in fact didn't even get published. They were basically crap. Then he switched to strings and was suddenly a hotshot, his first paper got cited by Nathan Seiberg and so on. Things worked out nicely for him after that. So I just have one simple question: how was it possible for this guy to suddenly be so brilliant as a string theorist after being unable to rise above mediocrity in all the non-string research he had done previously? Isn't it true that people who work on string theory and are able to make routine contributions to it are handed a cloak of brilliance by the powers that be, regardless of how mediocre they have shown themselves to be in their previous non-string research?

Finally, for the string theory commenters who are pretending not to know what Bee is talking about (because you understandably feel threatened by it), i leave you with my favorite rhetorical question:

In competition for funding and jobs, how many non-string single-author publications in Physical Review Letters does it take to outweigh just one paper by a string theorist in a regular journal (e.g. PRD) on which he/she is the junior author with 7 other more senior coauthors including his/her thesis advisor?Don't be wishy-washy now, tell us the number! (1? 5? 100? 10^500?)

It seems you're confusing the standard model (of particle physics) with the (cosmological) concordance model (also known as LambdaCDM). I know that (unfortunately) the latter has sometimes also been called the standard model, but it's really not a terminology that is much in use (and certainly not one that should be used).

"It seems you're confusing the standard model (of particle physics) with the (cosmological) concordance model (also known as LambdaCDM). I know that (unfortunately) the latter has sometimes also been called the standard model, but it's really not a terminology that is much in use (and certainly not one that should be used)."

Yes, this confusion does happen. Actually, "standard model" is a standard term in cosmology---to refer to the standard cosmological model. As to why that should be unfortunate, I don't know, unless it causes confusion.

Both terms were originated by Steven Weinberg (one of the few people who has done work in both traditional particle physics and traditional astronomical cosmology (as opposed to astroparticle physics, early universe, nucleosynthesis, inflation, etc---all of which are essentially particle physics done in the early universe and have only slightly more to do with cosmology than quantum theory in curved spacetime has to do with quantum gravity). Actually, he used it for the cosmological standard model first (which, in detail, was not then what it is now) and shortly thereafter for the standard model of particle physics.

Well, it's unfortunate that there should be two models with the same name, don't you think? I have encountered 'standard model' to mean the concordance model, but rarely so (and increasingly rarer in the last 10 years). So I think it would make sense to stop referring to it in this way just to avoid confusion.

"So I think it would make sense to stop referring to it in this way just to avoid confusion."

Well, it's you against Steven Weinberg. :-|

Seriously, I sometimes am annoyed by the confusion as well, especially since the level of confidence in each model changes differently as a function of time, and people confuse strengths and weaknesses of one with those of the other.

In cosmology, "standard model" is still used. These days, people often refer to the current standard model, LambdaCDM. However, in many cases why they really mean is the general standard model ("the hot big bang"), and not the details of LambdaCDM.

One could say that evolution is the standard model of biology, plate tectonics the standard model of geology, and so on, though the term isn't used in those fields in that way.

Despite being somewhat younger, "standard model" is more established in particle physics, so maybe there is some hope that people will stop using it in cosmology, especially now when the cosmological standard model (the hot big band) is essentially universally accepted and the debate is about modifications of or extensions to LambdaCDM.

Another difference is that in the standard model of particle physics, everything is more or less equally certain. While that is true of the standard model of cosmology in the narrow sense (the hot big bang), various aspects, which are sometimes unfortunately lumped in, are less certain: inflation, the nature of dark energy, details of structure formation, etc.

I agree. String theory needs to start producing viable predictions or it needs to be seriously modified (that's me saying it lightly). Aside from other assumptions string theorists make, the superpartners search makes me want to scream. "Oh, we didn't find them in this energy range. Let's move that upper bound and say we will find them in this higher range..." If your theory has no upper bound in your predictions then you're not doing science properly. You can't keep moving the goalposts when there is something obviously wrong with your gameplay. LQG has some untestable portions of its theory, but at LEAST we can test it reasonably since it comes right out of General Relativity. Start at lower, obtainable energies -- not high, unobtainable energies like string theory does.

As the Feynman once said... "it doesn't matter how beautiful your theory is. If it doesn't agree with experiment, it's wrong."